mirror of
https://github.com/openssl/openssl.git
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68 lines
2.2 KiB
Plaintext
68 lines
2.2 KiB
Plaintext
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=pod
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=head1 NAME
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SSL_read - Read bytes from a TLS connection.
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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int SSL_read(SSL *ssl, char *buf, int num);
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=head1 DESCRIPTION
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SSL_read() tries to read B<num> bytes from the specified B<ssl> into the
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buffer B<buf>. If necessary, SSL_read() will negotiate a TLS session, if
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not already explicitely performed by SSL_connect() or SSL_accept(). If the
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peer requests a re-negotiation, it will be performed transparently during
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the SSL_read() operation. The behaviour of SSL_read() depends on the
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underlying BIO.
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If the underlying BIO is B<blocking>, SSL_read() will only return, once the
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read operation has been finished or an error occured.
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If the underlying BIO is B<non-blocking>, SSL_read() will also return,
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when the underlying BIO could not satisfy the needs of SSL_read()
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to continue the operation. In this case a call to SSL_get_error() with the
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return value of SSL_read() will yield SSL_ERROR_WANT_READ or
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SSL_ERROR_WANT_WRITE. As at any time a re-negotiation is possible, a
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call to SSL_read() can also cause write operations! The calling process
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then must repeat the call after taking appropriate action to satisfy the
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needs of SSL_read(). The action depends on the underlying BIO. When using a
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non-blocking socket, nothing is to be done, but select() can be used to check
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for the required condition. When using a buffering BIO, like a BIO pair, data
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must be written into or retrieved out of the BIO before being able to continue.
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=head1 RETURN VALUES
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The following return values can occur:
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=over 4
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=item E<gt>0
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The read operation was successfull, the return value is the number of
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bytes actually read from the TLS connection.
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=item 0
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The read operation was not successfull, probably because no data was
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available. Call SSL_get_error() with the return value B<ret> to find out,
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whether an error occured.
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=item -1
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The read operation was not successfull, because either an error occured
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or action must be taken by the calling process. Call SSL_get_error() with the
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return value B<ret> to find out the reason.
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=back
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=head1 SEE ALSO
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L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_write(3)|SSL_write(3)>,
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L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>
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=cut
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